Spinal column support system

ABSTRACT

A spinal column support system, including a bone screw with an axially displaceable embodiment arranged above the bone screw shaft, a plate or rod arrangement with at least one opening into which the bone screw is screwed and an upper and lower disc which are mounted in the plate or rod at a distance from each other one over the other in a displaceable and positionable manner, and each including a hole through which the bone screw ( 16 ) is passed.

TECHNICAL FIELD

The present invention relates to the field of spinal column supportsystems. These serve to cure or alleviate spinal column problems orspinal column disorders. More precisely, the invention relates to asystem, wherein single vertebrae are either securely fixed via aplate/screw system or have a limited degree of residual movement withrespect to each other within a defined movement space.

PRIOR ART

In the systems currently found on the market, the vertebrae are fixedlyconnected to each other via a support system. These systems alwaysrequire a straight line for all of the screws screwed into theindividual vertebrae, so that the connection rods or connection platescan be integrated therein. In practice, this is not possible owing tothe arrangement and variety of human vertebrae and the degree ofaccuracy that the surgeon can achieve. The screws can be forced intoalignment by means of only one operation in spinal biomechanics, whichin fact is not generally desired, in that different vertebrae arerotated by means of a protruding screw. Permanent, undesired clamps arethus implanted in the spinal system.

Moreover, the geometry of the used circular rods provides a poor staticsupporting function. Circular rods are not used as supports in industry.

An example of a known support system, wherein the vertebrae are securelyfixed, is described in DE 195 10 543 C2. A screw comprises a bone screwshaft at one end and a threaded section at the other end, a nut-likebase plate being screwed onto the threaded section. The base platecomprises a groove on the surface opposite the bone screw shaft, anattachment bar can be inserted into the groove for the purposes ofconnecting to another such device.

In current rod and slot systems, a screw and the vertebra fixedlyconnected thereto are rotated such that the screw is accommodated in thenarrow slot or rod line. By reason of this, there are no simple startingsituations for the surgeon because he does not know which forces travelinto the spinal column system and how they are acting. As a result, thepatient can suffer permanent pain for a long time.

A spinal column support system is known from WO 95/27444 A1 andcomprises an elongated longitudinal plate arrangement havinglongitudinal slots in each of which a bone screw is disposed in adisplaceable manner. Hemispherical nuts provided with eccentric openingsare located on the bone screw above and below the plate arrangement andare tightened with the plate arrangement by a counter-nut. Only thetilting movement of the plate arrangement is adjustable by rotating thehemispherical nuts. The hemispherical nuts cannot be attached easilywhich means the system cannot have a wide variety of applications.

A series of very important requirements are placed upon a suitable andgood biomechanical vertebrae support system, i.e., adapted particularlyto human anatomy, and upon the possibilities of adjusting and aligningthe vertebrae screws in the operating room:

-   -   The bone screws used must have a good resistance to being pulled        out.    -   They must be able to be removed at a later date if need be.    -   The exiting part of the screw must be constructed in such a        manner that certain inclined positions of the bone screw can be        corrected.    -   Therefore, the bone screw must be multi-axial.    -   At the transition of the bone screw to a perpendicular support        plate, the screw must have a degree of movement so that the        vertebra can effect small conical movements in the        intervertebral disk region.    -   Therefore, the ideal bone screw must be multi-axial and have a        small degree of conical movement.    -   The perpendicular support system must be a plate system in which        a very narrow gap is not provided for receiving screws but        rather a zone is provided in which the bone screw can be fixedly        screwed in a perpendicular manner.    -   Minute adjustments of the vertebrae spacing before the final        tightening is likewise a great help for the surgeon and patient.

The currently known systems do not fulfill all of these requirements,wherein the complicated anatomical conditions and the exact placement ofthe bone vertebrae screws, which cannot be achieved, are the decidingfactors.

ILLUSTRATION OF THE INVENTION

It is thus the object of the invention to create a vertebrae supportsystem that overcomes these difficulties and obviates the negativeinfluencing factors on the spinal column system and has a positiveinfluence on the healing process in addition to the purely supportingfunction.

This object is achieved for a spinal column support system by thefeatures of Claim 1. Advantageous developments of the spinal columnsupport system in accordance with the invention are the subject matterof the dependent Claims.

A spinal column support system in accordance with the invention thuscomprises a bone screw which is formed so as to be able to move in anaxial manner above the bone screw shaft, a plate or rod arrangementhaving at least one opening in which the bone screw is screwed, as wellas an upper and a lower disk that are accommodated in the plate or rodat a spaced distance one above the other so as to be able to bedisplaced and positioned and that each comprise a hole, through whichthe bone screw passes.

The upper and/or lower disks are provided with eccentric, i.e., notdisposed on the central axis of the disks, holes, for example a circularbore and are attached so as to be rotatable. For this purpose circulardisks are, in an expedient manner, inserted and freely attached in theunits on the upper and lower sides of the plate or rod.

The lower disk advantageously contains a conical bore that is notlocated in the central axis thereof.

Owing to the free moveability of the disks and to the rotation thereof,the bores of the upper and lower disks can be attached in aperpendicular manner one above the other such that the upper part of thebone screw can be inserted in a perpendicular manner.

Owing to the fact that the bone screw is formed so as to be able to moveaxially above the bone screw shaft, the bone screw can always beattached by rotation or inclination, in a perpendicular manner, in theplate or rod system when the bone screw shaft is located in animprecisely defined position in the vertebra of the patient. In thismanner, the bone screws can stabilize the vertebrae bones in a tension-and force-free manner with respect to each other.

A vertebrae support system in accordance with the invention is thusformed as a plate having suitable openings and transverse stabilizers,so that the bone screws to be attached can be fixedly screwed,regardless of how they protrude from the vertebrae bone, using twocircular disks in which eccentric circular holes are located. The bonescrews themselves are additionally formed so as to be multi-axial in theupper part and thus permit extreme inclined positions of the vertebraebone screws.

The plate openings are designed in an expedient manner such that theyconsist of a rectangle or square, with the short sides in each casebeing replaced by semicircles (longitudinal hole), that are located onthe lower side and on the upper side of the plate.

In one advantageous exemplified embodiment of the spinal column supportsystem in accordance with the invention, the bone screws are formed in amulti-axial manner and an adjusting screw forming the upper part of thebone screw is coupled to the bone screw via a ball bearing system. Theadjusting screw is always inserted into the plate system in aperpendicular manner, wherein the adjusting screw can be inserted byfreely attaching the upper and lower circular disks in a force-freemanner. By tightening the nuts, the entire system can be coupled andadapted in a force-free manner to the vertebrae to be supported andattached.

A second type of bone screw is practically identical with the exceptionthat in the screwed condition the vertebrae bone still has a defineddegree of residual movement.

In contrast to the current systems found on the market, wherein the bonescrews always have to be screwed into the vertebrae bones in a preciselinear alignment, so that a screw connection via a rod system or anarrow slot-like plate is generally possible, the plate in accordancewith the invention and the screws associated therewith ensure that evenwith extreme exiting positions of the vertebrae bone screws, thesescrews can be fixedly screwed into the plate without even the smallestadditional application of force.

A preferred embodiment of the invention is characterized in that thesupport plate is assembled from modularly identical functional units.This means that according to the number of vertebrae to be supported,the plate can be extended by identical units. This produces a verystable form with zones acting in a defined resilient manner. The plateelements are formed such that the shape of the openings with theirinner-lying support ring receive the upper round disk and the lowerround thicker disk and can be arbitrarily displaced and positionedtherein. By rotating the lower disk (followed by the upper disk), theconical hole located therein can be freely positioned in order to insertthe adjusting screw. When the nut is tightened, the spherical head ofthe bone screw as well as the upper plate and the lower plate arefixedly clamped to the inner-lying support ring. The lower and the upperdisks can then no longer be displaced. The bone screw is likewiseattached, wherein the spherical coupling element between the bone screwand adjusting screw is locked by inserting the adjusting screw into theconical bore of the lower disk.

Accordingly, the surgeon can attach the placed bone screws in the platesystem without applying forces onto the vertebrae system.

A further preferred embodiment of the stabilizer in accordance with theinvention is the so-called semi-rigid spinal column support system. Thisconsists of the fact that the bone screws have a calotte system disposeddirectly behind the multi-axial joint, which calotte system permits thefront part of the bone screw and thus the part screwed into the bone tohave conical or pyramid-like free movement. This small amount of freemovement for the supported vertebrae stimulates the circulation ofblood, which has a positive effect on the healing process. The calottejoint is in an ideal manner disposed directly on the vertebrae joint andsupports this latter in a moveable manner in a restricted region. Thecalotte element also preferably contains a stepped torsion protector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the plan view of a first exemplified embodiment of a spinalcolumn support system in accordance with the invention in a rigidembodiment;

FIG. 2 shows a lateral view of the spinal column support system of FIG.1;

FIG. 3 shows the plan view of a second exemplified embodiment of aspinal column support system in accordance with the invention in asemi-rigid embodiment;

FIG. 4 shows a lateral view of the spinal column support system of FIG.3.

DESCRIPTION OF PREFERRED EXEMPLIFIED EMBODIMENTS

The invention will be described in more detail hereinafter with the aidof two exemplified embodiments. However, this illustration does notserve to limit the invention to the definitively described combinationof features, nor is the invention to be limited to the combination offeatures provided in the dependent Claims.

Reference is first made to FIGS. 1 and 2 that show a first exemplifiedembodiment in the form of a rigid spinal column support system. A plate2 comprises an elongated opening 4. Two circular disks, an upper disk 6and a lower, thicker disk 8, disposed one above the other at a spaceddistance, are accommodated in the opening 4 in alongitudinally-displaceable and rotatable manner. The disks 6, 8 eachcomprise eccentrically disposed holes 10, 12, the lower one of which isformed in a conical manner, i.e., it is wider at the bottom. Resilientzones that are formed as a bending point 14 are located between suchunits of the plate 2.

A bone screw 16 having an upper part 18 and a lower part 20 that isformed in a moveable manner with respect to the upper part is guidedthrough the holes 10, 12 and is attached, i.e., fixedly screwed, in theregion of the upper part. The upper part of the bone screw 16 is formedas an adjusting screw 18 with an adjusting body 18 a in the illustratedexemplified embodiment. The lower part of the bone screw 16 is theactual bone screw shaft 20. On the upper end, the bone screw shaft isprovided with a spherical head 22 that is accommodated in the adjustingbody 18 a in a rotationally movable manner. A nut 24 serves to attachthe arrangement, which nut on the one hand fixedly secures the sphericalhead 22 in the adjusting body 18 a and on the other hand fixedly securesthe two disks 6, 8 in the plate 4.

By displacing and rotating the two disks 6, 8 for aligning the spinalcolumn support system after insertion of the bone screws into thevertebrae bones, it is possible to compensate for inclined positions ofthe bone screw, i.e., of the bone screw shaft 20. The fact that the bonescrew 16 with its two parts 18, 20 is disposed so as to be multi-axialimparts additional flexibility to the arrangement.

A second exemplified embodiment of the invention in the form of asemi-rigid spinal column support system will be described with the aidof FIGS. 3 and 4. The parts which are the same as those in the firstexemplified embodiment will not be described again.

In this exemplified embodiment, the bone screw shaft 20 does notterminate directly in the spherical head 22 but rather there isadditionally provided a holding device (holding element) 26 that isformed as a calotte system and in turn is disposed in a moveable manner.The holding device 26 terminates at its upper end in the spherical head22 and consists of a calotte body 28 that comprises a calotte bearing 30on the lower side. The upper end 20 a of the bone screw shaft 20 ismounted in the calotte bearing 30 in a conical or pyramid-like freelymoveable manner. A stepped torsion protector 32 is provided in thecalotte body 28.

Owing to the additional freedom of movement of the supported vertebraethat is possible to a small extent, circulation of blood is stimulatedand the healing process is accelerated.

1. Spinal column support system comprising a bone screw (16), a plate orrod arrangement having at least one opening (4) in which the bone screw(16) is displaceable, an upper and a lower rotatable fixing element thatcan be positioned at a spaced distance one above the other with respectto the plate (2) or rod and that each comprise an eccentrically disposedhole (10, 12), through which the bone screw (16) passes, characterizedin that the bone screw (16) is formed so as to be able to move axiallyabove the bone screw shaft and an upper and a lower disk (6, 8) are eachprovided as the fixing elements, which disks are accommodated in theplate (2) or rod in a displaceable manner and each comprise aneccentrically disposed hole (10, 12).
 2. Spinal column support systemaccording to claim 1, characterized in that the plate or rod is providedwith a support ring in the inner wall of the opening, which support ringaccommodates the upper and the lower disks.
 3. Spinal column supportsystem according to claim 1, characterized in that the upper and thelower disks (6, 8) are circular.
 4. Spinal column support systemaccording to claim 1, characterized in that the lower disk (8) isthicker than the upper disk (6).
 5. Spinal column support systemaccording to one of claims 1 through 4, characterized in that the hole(12) of the lower disk (8) is conical.
 6. Spinal column support systemaccording to claim 1, characterized in that the bone screw (16) consistsof an upper part (18) that is provided for screwing in the plate (2) orrod and comprises a spherical receptacle on the lower end, and of alower bone screw shaft part (20) that comprises, on the upper end, aspherical head (22) that is accommodated in the spherical receptacle ina rotationally moveable manner.
 7. Spinal column support systemaccording to claim 6, characterized in that the bone screw shaft part(20) is provided with a holding element (26) on the upper end, whichholding element comprises, on the upper end, the spherical head (22)accommodated in the upper bone screw part in a rotationally moveablemanner and also comprises a calotte bearing (30) beneath the sphericalhead for receiving the upper end (20 a) of the bone screw shaft part(20), in such a manner that the bone screw shaft part is freely movablein the calotte bearing in a conical or pyramid-like manner.
 8. Spinalcolumn support system according to claim 7, characterized in that astepped torsion protector (32) is provided in the calotte bearing (30).9. Spinal column support system according to claim 1, characterized inthat the upper part of the bone screw is an adjusting screw (18) that isprovided with a thread on its end opposite the bone screw shaft (20) andcan be attached by means of a nut (24).
 10. Spinal column support systemaccording to claim 1, characterized in that one or several units areprovided as an extension for supporting one or several vertebrae. 11.Spinal column support system according to claim 10, characterized inthat a bending zone (14) is provided between adjacent units.